The invention relates to a combined night/day viewing apparatus for armoured vehicles. A single housing contains a first movable input reflector and a second input reflector for causing the input light beams originating from the field of view to deviate in the direction of the optical axis of the night path and of the day path, respectively. The night path is constituted by an objective, a light intensifier tube and a bent ocular and the day path is constituted by an optical system having an enlargement 1 (no magnification) and comprising at least one second output reflector.
The viewing apparatus according to the invention is such that the enlargement is equal to 1 for the day path and is of the order of 1 for the night path. For both paths, attempts are made to obtain the largest possible field of view. Through this kind of apparatus, which is mounted so as to traverse the armouring of a vehicle, the viewing is periscopic. The invention is used especially for an episcope intended for driving a tank.
French Utility Models Nos. 2,377,647 and 2,377,648 disclose a night and day viewing apparatus, that is to say an optical periscopic apparatus contained in a single housing that can operate for all the degress of illumination of the objective observed both with a bright sky and with a clouded sky by night. When such an apparatus is mounted in an armoured vehicle, it can consist of a hermetic assembly that can be received by the standardized opening provided until now, which can receive both night viewing apparatus and day viewing apparatus. These technical characteristics and these functions are also examined at the beginning for the viewing apparatus described below. It is in fact very disadvantageous in both cases to use immovable and distinct optical apparatus for viewing by night and by day especially because of the necessity on the one hand to proceed to switching operations, during which viewing through the optical apparatus is no longer possible, and on the other hand to have to arrange the apparatus not utilized without risk of damage of the latter or congestion of the dwelling-place of the vehicle, which is tiny.
The compact construction in a single housing of standarized dimensions can be comparatively readily obtained in a viewing apparatus for which the fields of view are narrow, i.e. of the order of 5.degree. to 10.degree., and for which the enlargements obtained are substantial, i.e. of the order of 5 to 10, the vehicle provided with the viewing apparatus being normally stationary during viewing. On the contrary, viewing especially for driving a vehicle has to be effected with normal vision, i.e. for a small enlargement equal or substantially equal to 1, which leads to a large field of view. A largest possible field of view is desired and it has to be ensured that the compact construction obtained due to the fact that a night viewing apparatus and a day viewing apparatus are combined in a single housing is not accompanied by a reduction of the field of view.